This invention relates to a tire assembly for a two-wheeled vehicle, and more particularly to a tire assembly to be used as a front and a rear wheel for a two-wheeled vehicle and having a belt construction improved to obtain best stability and traveling performance when traveling at high speeds.
For example, radial tires have been used for front and rear wheels of two-wheeled vehicles. In order to improve the stability of, for example, radial tires when traveling, a belt layer to be interposed between a tread and a carcass consists of a plurality of nylon belt layers made of nylon cords arranged with different widths to form steps by narrowing their widths progressively from the carcass to the tread. Such steps of belt layers narrowing their widths from the carcass to the tread are referred to hereinafter as a "positive step". However, this arrangement is disadvantageous because of insufficient rigidity of the belt.
In the case where sporty traveling performance is important, it is needed to improve braking capacity, stability in acceleration and gripping performance in turning. Therefore, in order to increase the belt rigidity, a Kevlar belt layer made of Kevlar cords must unavoidably be used in positive steps at the sacrifice of cost and durability.
In order to improve the rigidity of the nylon belt for a tire, moreover, it can be conceivable that the belt is made in three layers. With a tire for a front wheel, however, when shoulder portions are thick having more than three layers, the rigidity of the shoulder portions becomes excessively high. As a result, it is difficult to obtain self-aligning of tires in negative directions to supplement camber thrust for tires for a two-wheeled vehicle in banking. Therefore, a rider of the two-wheeled vehicle is required to modify the vehicle position by pulling a handle bar in the banking direction. Accordingly, smooth handle operation is detrimentally affected. Moreover, when the rigidity of the shoulder portions is higher, a particular phenomenon of radial tires referred to as "chattering" is likely to occur. This is the jumping up of a vehicle body.
With tires for rear wheels, a belt construction having the usual positive steps is particularly poor in rigidity of shoulder portions. Therefore, stability in full-banking and sufficient rigidity in acceleration under a banked condition when returning from cornering could not be obtained so that reaction capacity is lowered.